I think, but am not 100% sure that this might have changed
I tried "search" and of course can't find the post that talked about it, but checking mousesavers it says:
You can book one room per adult Annual Pass. You can book with a valid Annual Pass, an exchange voucher or with the intent to purchase an Annual Pass, as long as you present a valid Annual Pass or exchange voucher upon check-in.
and allears says:
If I am an AP holder, can I book more than one room at the AP rate?
Not any longer. It is now one discounted room per passholder.
Hopefully someone else who recently booked using their AP can advise if this is still in effect